Process of stripping tin.



No. 791.555. PATENTED JUNE6-,1905.

I H. W. HEMINGWAY.

PROCESS OF STRIPPING TIN.

APPLICATION FILED OCT. 29, 1902.

WIT/VIJSES. awn/70k:

v ii-0 1m UNITED STATES Patented June 6, 1905.

PATENT OFFICE.

PROCESS, OF STRIPPING TIN.

SPECIFICATION forming part of Letters Patent No. 791,555, dated une 6,1905.

Application filed October 29, 1902. Serial No. 129,315.

To all whom it may concern:

Be it known that I, HENRY WILLIAM HEM- INGWAY, a subject of the King ofGreat Britain and Ireland, residing at Albyns, Forest Road, Walthamstow,Essex, England, have in-- vented a certain new and useful ImprovedProcess of Stripping Tin from Tinned Iron, Recovering the RespectiveMetals, and Obtaining Nitric Acid as a By-Product, of which thefollowing is a specification.

In the specification to my Letters Patent dated December 4, 1900, No.663,024, is described a process in which tinned iron istreated with asolution of persulfate of iron, the tin being precipitated as asulfid,whence the metal is recovered. r

According to my improved process, thesubject of my present invention, Istill employ a solution of persulfate of iron as an agent for strippingthe tin; but I make the solution slightly acid and treat itelectrolytically, the tin being deposited in a metallic state upon anysuitable cathode. When the electrolyte becomes inactive, I treat it withnitrate of soda (or of potash) in conjunction with sulfuric orhydrochloric acid with a view to its revivification.

The accompanying drawing represents apparatus adapted for use incarrying out my' improved process. I

The tinned iron clippings or like scrap are immersed in a bath ofpersulfate of iron contained in the tank A, said bath being suitablyacidified by the addition of any mineral acid; but sulfuric acid ispreferred. The tin having become dissolved, a valve a in the pipe a isopened and the liquor run into the vessel B, where it is treatedelectrolytically, the electrodes 0 consisting, preferably, of an ironanode and a copper or tinned copper cathode. The tin or the greaterportion thereof having been deposited upon the cathode, the electrolyteis passed by way of the pipe 6, controlled by the valve 7), to thevessel D, where nitrate of soda, (or of. p0tash,) either alone or inconjunction with sulfuric acid, is added. The efficacy of the liquor ishereby restored and the liquor rendered suitable for reuse instrip pinga further quantity of tinned iron. For

the mixture of nitrate and sulfuric acid other oxidizing agents may besubstituted. The

vessel D is provided with a jacket M for heating the liquor and with anoutlet F for carrying ofi the nitrous fumes. The electrolyte having beensufiiciently oxidized, the valve d in the pipe d is opened and theliquor allowed to run into the tank L, whence it is returned by the pumpN or by equivalent means to the tank A.

When it is deemed desirable to reduce to a minimum the quantity ofpersulfate of iron employed, the tin-scrap may be added direct to asolution of nitrate of soda (or of potash) mixed with sulfuric acid, thetin going into solution for ultimate recovery by electrolytic or othermeans.

What I claim as my invention, anddesire to secure by Letters Patent, is

The herein-described process for stripping HENRY WILLIAM HEMINGWAY.

Witnesses: WM. 0. BROWN,- FRED 0. SMITH.

